Heater - Poor Output or Overheated Engine Diagnosis
83VW03Applies To VW 4 cyl... engine
All watercooled
Group
19
Subject:
Engine
Part Identifier N/A
Key Points
Diagnosis/repair - - Overheated engine or poor heater output
C
Number
83-04
June 8, 1983
Engine overheating or insufficient heater output are often not caused by defective thermostats or thermoswitches. To avoid unnecessary parts replacements, proper diagnosis of complaints must be followed.
Diagnosis/Repair - - Overheating
Work sequence
Note
Before checking car, discuss problem with customer.
^ Engine temperature when driving in "stop and go" traffic will be higher than normal due to lack of air circulation around engine and radiator. Temperature gauge needle may reach almost into the red zone under such conditions. However, at highway speeds, the temperature should return to normal (half scale or a little higher).
For abnormal operation (needle of temperature gauge in red zone), proceed as follows:
- check coolant level
^ if low, top up and check for leaks using tool VW 1274 for pressurizing cooling system. Repair as required.
CAUTION
Do not perform pressurized test at expansion tank of Dasher models up to 1980 M.Y. Apply tester on radiator only.
- check antifreeze protection
^ if lower than -40~ F (-40~C) on gauge, increase ratio of water-to-antifreeze until gauge reads -40~F or higher (-40~F occurs with 50/50 solution)
- run engine until coolant reaches operating temperature
- feel top and bottom of radiator
^ if both are hot, thermostat is OK
^ if bottom is cool, replace thermostat
If antifreeze protection was OK and radiator was warm top and bottom, then ONLY
- replace thermoswitch.
Diagnosis/Repair - - Insufficient heater output
Work sequence
- check antifreeze protection and adjust if necessary not lower than -40~F (-40~C)
- remove thermostat and check for sand particles on inside of thermostat housing
^ if sand is found, clean cooling system
- remove coolant pump
- remove all coolant and heater hoses from engine
- flush radiator, engine and heater
- reassemble all parts removed
- re-install thermostat
^ use OLD thermostat if sand particles were not found
^ install NEW thermostat if sand was found in housing
- road test vehicle